The present invention relates to a molding device and a molding method. More particularly, it relates to a molding device and a molding method for producing an optical semiconductor device, e.g., one used for an IrDA (Infrared Data Association) module.
Optical semiconductor devices for transmitting or receiving infrared rays have been used for digital assistant and notebook-sized personal computer-equipped IrDA modules which are used to carry out radio (infrared rays) data communication. Such optical semiconductor devices include lens parts, and are molded with mold resins and then packaged to be used. To mold these optical semiconductor devices, molding devices which are capable of obtaining molded articles with high dimension accuracy have been used. These molding devices are used to mold articles by injecting mold resins from gates into cavities formed by the molds. Since the gates of the molding devices control flow rates of mold resins flowing into the cavities and the filling status within the cavities, whether or not molding articles are successful depends to a large degree on the shape of the gates and their positions.
Particularly, if the shape and the position of the gate of the molding device is not appropriate for the respective cavity, bubbles or voids may be caused in the mold resin when the mold resin is injected. Should such bubbles or voids remain in the finished package, especially in a lens part, optical characteristics for transmitting and receiving infrared rays emitted from an optical semiconductor device may be adversely affected. Further, the occurrence of a weld line (junction line) may cause cracks in addition to being undesirable to the appearance of the final product. Various arrangements of the gate have been considered to remove this defect.
For example, FIGS. 12(a) and 12(b) show examples of a gate 102 that is provided on only one side of a cavity member 100. In such cases, a mold resin sequentially flows within member 100 without admitting air in the mold resin so that the cavity 100 can be filled with mold resin, which leads to an article free from defects. Consequently, in either case, few failures occur on a hemispherical portion 104 which is closer to the gate 102 because of the pre-injection of the mold resin into the hemispherical portion 104 which is closer to the gate 102. There has been a problem, however, that a void (voids) 108 may be formed on a hemispherical portion 106 which is further from the gate 102 due to air admitted in the mold resin caused by the flow of the mold resin.
Further, FIGS. 13(a) and 13(b) show examples of gates 112 that are provided on both sides of a cavity member 100. The gates 112 are respectively arranged adjacent a pair of hemispherical portions 110. Accordingly, simultaneous injection of the mold resins into the hemispherical portions 110 can produce failure caused by voids which may occur on the hemispherical portions 110. One problem that may occur, however, when using this approach is that a weld line 114 may be formed between the pair of hemispherical portions 110 where the mold resin merged. Such a weld line might cause further cracks in addition to being undesirable in appearance.
Next, as shown in FIGS. 14(a) through 14(c), there is a method that a plate-like gate 116 is disposed on a cavity member 100. For example, as the shape of a longitudinal cross section of the plate-like gate 116 is shown in FIG. 14(b), an inclination is provided on the upper surface side of the gate 116 to allow the injected mold resin (not shown) to be directed accurately to the receiving hemispherical portions 110. In this case, no failures, voids, etc. occurred on the hemispherical portions 110. However, a large void (or voids) 120 may form on a portion where the mold resin introduced from the lower side of an optical semiconductor element 118 disposed within the cavity member 100 is reversed, or form on a portion where the mold resin introduced from the lower side of the semiconductor element 118 engages the mold resin injected from the upper side of the semiconductor element 118.
Using the longitudinal cross section of the gate shown in FIG. 14(c) for injecting the mold resin directly into the cavity 100 from the plate-like gate 116 without the shown inclined inner surfaces may result in the formation of voids 122 on the upper part of the hemispherical portions 110 or on the optical semiconductor element 118. No weld lines as occurred between the hemispherical portions 110 in FIGS. 13(a) and 13(b) were observed.
It is an object of the present invention to provide a molding device and a molding method which do not leave voids, weld lines or the like in a molded article, particularly when an optical semiconductor element is molded using a mold resin.
According to one aspect of the invention, there is provided a molding device comprising a cavity having first and second parts, at least one of the parts including at least one concave portion therein for molding an article having at least one convex portion therein, and a gate for injecting mold resin into the first and second parts of the cavity, the gate including at least one gate side portion for directly the mold resin into the part of the cavity having the at least one concave portion for molding a portion of the article having the at least one convex portion, and at least one plate-like gate base for injecting the mold resin in a substantially flat sheet state into the other part of the cavity for molding the other portion of the article.
According to another aspect of the invention, there is provided a method for molding an article, the method comprising the steps of providing a molding device having first and second parts defining a cavity, at least one of the parts including a concave portion, injecting mold resin into the concave portion of the at least one of the parts for molding a portion of the article including at least one convex portion, and injecting mold resin into the other of the first and second parts for molding another portion of the article having no convex portion, the injecting the mold resin into both of the first and second parts occurring substantially simultaneously.